The long-term objective of this project is to understand the various intracellular factors that regulate steroidogenesis. The proposed studies focus on two key enzymes in the production of steroid hormones. The first is the cholesterol side chain cleavage enzyme (P450scc), which carries out the rate-limiting step in the production of steroid hormones. The second enzyme is P450c17, which serves as a key branch point in the production of the different classes of steroid hormones. The proposed studies focus on the transcriptional regulation of the human genes for P450scc and P450c17. The proposed experiments will use human placental JEG-3 cells and human adrenal NCI-H295 cells to study placental- and adrenal-specific expression. Alternative approaches are proposed to clone newly identified transcriptional regulatory proteins, followed by studies to document function in expression studies.